A deep-earth plumbing system beneath Hawaii

Lava splatter near the coastal entry of Kilauea.
[Image courtesy of Pete Mouginis-Mark, Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa]

The Hawaiian islands have formed as the Earth's crust moves over a "hotspot" where magma is rising up to the surface. Scientists have debated over how this hotspot works and how deep into the Earth it reaches, but a new study may help clear things up.

There are two leading ideas about this hotspot. It might be caused by a giant plume of magma rising from very deep in the mantle. Or, it might the result of magma circulating much closer to Earth's surface.

Pahoehoe lava flow at Kilauea.
[Image courtesy of Pete Mouginis-Mark, Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa]

Cecily Wolfe of the University of Hawaii and colleagues figured that seismic activity around Hawaii might have something to tell them about this problem. Seismic waves travel through the mantle at different speeds, depending partly on whether they are moving through molten magma or solid rock. The researchers analyzed information from a large array of devices that monitor seismic activity, located on the ocean bottom and on land.

The results support the first idea, that a plume of magma is rising from the Earth's lower mantle, beneath the Hawaiian hotspot. This research appears in the 4 December issue of the journal Science.